Synthesis, characterization and diastereoselective coordination of a planarly chiral, hybrid ferrocene ligand, (Sp)-2-(diphenylphosphino)ferrocenecarboxylic acid

Article abstract of DOI:10.1039/b109495p

Hydrolytic cleavage of the dihydrooxazole ring in (S_p)-2-{2-(diphenylphosphino)ferrocenyl}-4-(1-methylethyl)-4, 5-dihydrooxazole affords the planarly chiral functionalized phosphine, (S_p)-2-(diphenylphosphino)-ferrocenecarboxylic acid, (S_p)-Hpfc, in two steps and 65% yield. (S_p)-Hpfc, all intermediates and the corresponding phosphine oxides were characterized by elemental analysis, multinuclear NMR and IR spectroscopy, and by optical rotation measurements. Solid-state structures of the phosphine oxides were further studied by X-ray crystallography to reveal extensive hydrogen bonding of various types. Neutralization of (S_p)-Hpfc with tert-BuOK followed by metathesis of the in situ obtained salt with [{RuCl(μ-Cl)(η⁶-p-cymene)}₂] gives a chelate complex [RuCl(pfc-k²O,P)(η⁶-p-cymene)], 5, as a kinetic 1:1 mixture of diastereoisomers. Upon standing in solution, the diastereomeric mixture undergoes a spontaneous resolution to yield the thermodynamically preferred diastereoisomer (R_Ru,S_p)-5 whose configuration was corroborated by X-ray crystallography; the (R_Ru,S_p)-5 diastereoisomer was obtained in 82% yield by crystallization. The epimerization is likely initiated by a reversible Ru-O bond cleavage and suggests a hemilabile coordination of the (S_p)-pfc^- anion. However, according to NMR spectra pure (R_Ru,S_p)-5 does not undergo diastereoisomer interconversion in a solution, which is in agreement with an unfavourable geometric arrangement of the (S_Ru)-epimer.

Full text of DOI:10.1039/b109495p

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Synthesis, characterization and diastereoselective coordination
of a planarly chiral, hybrid ferrocene ligand,
(Sp)-2-(diphenylphosphino)ferrocenecarboxylic acid
Petr Stepnicka
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2,
Czech Republic. E-mail: stepnic@mail.natur.cuni.cz
Received (in Strasbourg, France) 17th October 2001, Accepted 5th December 2001
First published as an Advance Article on the web 16th April 2002
Hydrolytic cleavage of the dihydrooxazole ring in (Sp)-2-{2-(diphenylphosphino)ferrocenyl}-4-(1-methylethyl)-
4,5-dihydrooxazole affords the planarly chiral functionalized phosphine, (Sp)-2-(diphenylphosphino)-
ferrocenecarboxylic acid, (Sp)-Hpfc, in two steps and 65% yield. (Sp)-Hpfc, all intermediates and the
corresponding phosphine oxides were characterized by elemental analysis, multinuclear NMR and IR
spectroscopy, and by optical rotation measurements. Solid-state structures of the phosphine oxides were further
studied by X-ray crystallography to reveal extensive hydrogen bonding of various types. Neutralization of
(Sp)-Hpfc with tert-BuOK followed by metathesis of the in situ obtained salt with [{RuCl(m-Cl)(Z6-p-cymene)}2]
gives a chelate complex [RuCl(pfc-k2O,P)(Z6-p-cymene)], 5, as a kinetic 1 : 1 mixture of diastereoisomers.
Upon standing in solution, the diastereomeric mixture undergoes a spontaneous resolution to yield the
thermodynamically preferred diastereoisomer (RRu ,Sp)-5 whose configuration was corroborated by X-ray
crystallography; the (RRu ,Sp)-5 diastereoisomer was obtained in 82% yield by crystallization. The
epimerization is likely initiated by a reversible Ru–O bond cleavage and suggests a hemilabile coordination of
the (Sp)-pfcꢀ anion. However, according to NMR spectra pure (RRu ,Sp)-5 does not undergo diastereoisomer
interconversion in a solution, which is in agreement with an unfavourable geometric arrangement of the
(SRu)-epimer.
In spite of challenging advances in the synthesis and catalytic
applications of planarly chiral Z6-arene tricarbonylchro-
mium(0)1 and cymantrene2 complexes, enantioselective ho-
mogeneous catalysis with organometallic ligands is still
dominated by ferrocene compounds.3 Among others, the
development of chiral ferrocene ligands was initiated by the
discovery of selective ortho-metalation4 of (N,N-dimethyl-
aminomethyl)ferrocene5 and its diastereoselective variant
using C-chiral (1-ferrocenylethyl)dimethylamine (Chart 1, A).6
An approach combining successive ortho-lithiation=
functionalization and replacement of the dimethylamino group
resulted in the latter case in the synthesis of numerous ferro-
cene derivatives with mixed central and planar chirality (Chart
1, B), which were used as effective catalyst components, even
on the industry scale.7 Since then, other chiral directing groups
have been used to synthesize planarly chiral ferrocenes by the
diastereoselective ortho-metalation approach.8 More recently,
and very likely stimulated by successful applications of
dihydrooxazole-modified triphenylphosphine9 (Chart 1, C),
this methodology was extended to C-chiral ferrocene 4,5-
dihydrooxazoles (or oxazolines)10 to provide functionalized
ferrocene oxazolines11 (Chart 1, D), which were tested as
ligands in various transition-metal catalyzed reactions.12
However, besides being an excellent chiral auxiliary group,
the oxazoline ring may also be looked upon as a carboxyl-
protecting group, which can be built up from readily available
b-aminoalcohols and efficiently deprotected to give carboxylic
acids after a synthetic transformation of the protected mole-
cule.10a,13 In this way, application of the protecting group
approach towards 2-phosphinoferrocene oxazolines yields
phosphinocarboxylic acids,14 which have been successfully
applied in catalysis.15
We have recently reported the synthesis of 10-(diphenyl-
phosphino)ferrocenecarboxylic acid (Hdpf)16 and also
demonstrated its ability to bind transition metals in various
coordination modes.17 This article describes the preparation,
spectral characterization and solid-state structures of the pla-
narly chiral isomer of Hdpf, (Sp)-2-(diphenylphosphino)ferro-
cencarboxylic acid (Hpfc) and related phosphine oxide
derivatives. Furthermore, diastereoselective synthesis of a
ruthenium complex with an O,P-chelating pfcꢀ anion, [RuCl-
(pfc-k2O,P)(Z6-p-cymene)], is presented and factors influencing
the course of complex formation are discussed with respect to
the solid-state structure of the preferred diastereoisomer.
It should be noted that (Sp)-Hpfc has already been
reported twice as an intermediate in the synthesis of
Chart 1
DOI: 10.1039/b109495p
New J. Chem., 2002, 26, 567–575
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diamidodiphosphine ligands for allylic substitution—however,
full experimental details or characterization data were not
provided in either case.18
atoms are observed as phosphorus-coupled doublets whilst
the C5H5 resonance usually remains uncoupled. The signals
due to the diastereotopic phenyl rings appear as well resolved
doublets with the JPC scalar coupling constants similar to
those of triphenylphosphine and triphenylphosphine oxide,
respectively.20
Results and discussion
Syntheses and characterization
Solid-state structure of (S,Sp)-3
(Sp)-Hpfc was prepared by the standard oxazoline ring-open-
ing protocol19 from oxazoline (S,Sp)-1 (Scheme 1): the oxa-
zoline was first reacted with a trifluoroacetic acid–water
mixture in THF to give an unstable ammonium salt inter-
mediate, which was without isolation converted to a stable
ester amide (S,Sp)-2 using an acetic anhydride–pyridine mix-
ture (70% yield). A subsequent saponification of the ester
amide with 1 M sodium hydroxide in a ternary water–metha-
nol–THF mixture finally afforded (Sp)-Hpfc in 93% yield after
chromatography.
Possessing a defined reference chirality centre inherent in
(S)-valinol, the ester amide (S,Sp)-2 was considered suitable to
crystallographically confirm the configuration at the chira-
lity plane. However, repeated attempts to obtain X-ray quality
crystals met with no success since the compound tenaciously
forms a glassy solid upon recrystallization. Fortunately, this is
not the case of the analogous phosphine oxide (S,Sp)-3, which
was obtained by hydrogen peroxide oxidation of the parent
phosphine (Scheme 1). Similarly, the oxidation of (Sp)-Hpfc,
which is also obtained as a non-crystallizing orange solid
material, gives quantitatively the corresponding phosphine
oxide (Sp)-4, whose solid-state structure was determined.
All compounds were characterized by NMR and IR spec-
troscopy, elemental analyses and molar optical rotations. The
1H NMR spectra of all compounds show a set of resonances
typical for an unsymmetrically 1,2-disubstituted ferrocene
unit, consisting of a sharp singlet (C5H5) and three char-
acteristic multiplets due to the non-equivalent C5H3 protons.
In 13C NMR spectra, the signals of the ferrocene C5H3 carbon
The molecular structure of compound (S,Sp)-3 is shown in
Fig. 1 and selected geometric parameters are listed in Table 1.
Both the (S)-configuration at C(25) and Flack’s enantiomorph
parameter (see Table 4) corroborate the expected (Sp)-config-
uration at the ferrocene unit.
Compared to 10-(diphenylphosphinoyl)ferrocenecarboxylic
+
acid [P=O 1.487(2) A]16 and 1,10-bis(diphenylphosphinoyl)-
+
ferrocene [P=O 1.493(2) A],21 (S,Sp)-3 exhibits a shorter P–O
bond length. However, the other parameters describing the
geometry of the diphenylphosphinoyl moiety are similar in
all the mentioned compounds. The arrangement of the ester
amide side-chain is best described as consisting of two planar
parts, [C(11)C(1)O(1)O(2)C(24)] and [C(30)C(29)O(4)NC(25)]
(perpendicular distances of the plane-defining atom to the
+
least-squares plane are shorter than 0.20 A), which subtend a
dihedral angle of 15.7(3)ꢁ. Such an arrangement seems to be
brought about by the formation of an unsymmetric three-
centred hydrogen bonds between the amide hydrogen and
the O(2) and O(3) oxygen atoms [N–H(90)Á Á ÁO(3): NÁ Á ÁO(3)
+
2.868(3), N–H(90) 0.86(2) A, N–H(90)Á Á ÁO(3) 172(2)ꢁ; N–
+
H(90)Á Á ÁO(2): NÁ Á ÁO(2) 2.773(3) A, N–H(90)Á Á ÁO(2) 103(2)ꢁ].
The intramolecular hydrogen bonding that controls the
conformation of the ester amide side chain and very likely
accounts for the remarkably different crystallization abilities of
the phosphine-phosphine oxide pair (S,Sp)-2 and (S,Sp)-3,
leaves the ferrocene framework in (S,Sp)-3 virtually intact. The
carboxyl group plane is nearly coplanar with the adjacent
cyclopentadienyl plane, the dihedral angle of the Cp1 and
[C(11)O(1)O(2)] least-squares planes being 5.4(3)ꢁ. The ferro-
cene cyclopentadienyl rings adopt a close-to-eclipsed con-
formation as evidenced by the torsion angle t[C(1)–Cg1–Cg2–
C(10)] of ꢀ7.9(2)ꢁ and are tilted at a dihedral angle of 1.7(1)ꢁ.
Fig. 1 Structure of (S,Sp)-3 drawn at the 30% probability level. Ring
atoms are labelled consecutively, hence, labels of only pivot and
adjacent atoms are shown.
Scheme 1
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Table 2 Selected geometric data for compound (Sp)-4a
Table 1 Selected geometric data for compound (S,Sp)-3a
Fe–Cg1
1.642(1) Fe–C(Cp) ave.
1.650(1) C–C(Cp) ave.
1.458(2) O(3)–P–C(2,12,18) 109.4(1)–118.9(1)
2.04(1)
1.42(1)
Fe–Cg1
1.640(1) Fe–C(Cp) ave.
1.653(2) C–C(Cp) ave.
1.456(3) O(3)–P–C(2,12,18) 107.8(2)–119.1(2)
2.04(1)
1.42(2)
Fe–Cg2
P–O(3)
Fe–Cg2
P–O(3)
C(2)–P
P–C(12)
P–C(18)
1.801(2) C–P–Cb
102.6(1)–106.6(1)
129.4(2)
124.2(2)
C(2)–P
P–C(12)
P–C(18)
1.796(3) C–P–Cb
101.6(2)–105.3(2)
128.1(2)
125.1(2)
1.808(2) C(1)–C(2)–P
1.813(2) C(3)–C(2)–P
1.799(3) C(1)–C(2)–P
1.819(4) C(3)–C(2)–P
C(1)–C(11)
C(11)–O(1)
C(11)–O(2)
O(2)–C(24)
C(24)–C(25)
C(25)–C(26)
C(26)–C(27)
C(26)–C(28)
C(25)–N
1.482(3) O(1)–C(11)–O(2) 125.1(2)
1.210(3) C(5)–C(1)–C(11) 123.0(2)
1.336(3) C(2)–C(1)–C(11) 128.9(2)
1.462(3) C(11)–O(2)–C(24) 118.8(2)
1.513(4) O(2)–C(24)–C(25) 109.2(2)
1.543(4) C(24)–C(25)–C(26) 112.4(2)
C(1)–C(11)
C(11)–O(1)
C(11)–O(2)
C(11)–C(1)–C(2)–P
C(2)–C(1)–C(11)–O(1)
C(2)–C(1)–C(11)–O(2)
Cp1,Cp2
1.479(5) O(1)–C(11)–O(2) 125.3(3)
1.209(4) C(5)–C(1)–C(11) 126.8(3)
1.332(4) C(2)–C(1)–C(11) 124.7(3)
5.7(4)
ꢀ8.9(5)
170.7(3)
83.9(2)
78.2(2)
1.525(5) N–C(25)–C(24)
1.514(5) N–C(25)–C(26)
109.0(2)
113.6(2)
1.8(2) Cp1,Ph2
78.4(2) Ph1,Ph2
Cp1,Ph1
1.456(3) C(25)–C(26)–C(27) 112.2(3)
1.350(3) C(25)–C(26)–C(28) 109.6(3)
1.222(3) C(27)–C(26)–C(28) 111.2(3)
a
N–C(29)
C(29)–O(4)
C(29)–C(30)
Planes are defined as follows: Cp1, C(1–5); Cp2, C(6–10); Ph1, C(12–
17); Ph2, C(18–23). Cg1 and Cg2 are centroids of the cyclopentadienyl
b
1.508(4) C(25)–N–C(29)
N–C(29)–C(30)
O(4)–C(29)–N
122.5(2)
114.8(2)
123.7(2)
rings Cp1 and Cp2, respectively. C(2)–P–C(12,18) and C(12)–P–
C(18) angles.
O(4)–C(29)–C(30) 121.4(2)
C(11)–C(1)–C(2)–P
C(2)–C(1)–C(11)–O(1)
C(2)–C(1)–C(11)–O(2)
Cp1,Cp2
3.2(4)
173.6(2)
ꢀ8.0(3)
1.7(1) Cp1,Ph1
68.4(2) Cp1,Ph2
80.8(1)
84.2(1)
molecular, the molecules of phosphine oxide (Sp)-4 are
involved in intermolecular hydrogen bonding in which the
carboxyl OH group of one molecule is bonded to the phos-
phinoyl oxygen atom of a neighbouring molecule, thus form-
Ph1,Ph2
a
Plane definitions: Cp1, C(1–5); Cp2, C(6–10); Ph1, C(12–17); Ph2,
C(18–23). Cg1 and Cg2 are centroids of the rings Cp1 and Cp2,
respectively. C(2)–P–C(12,18) and C(12)–P–C(18) angles.
b
ing infinite chains parallel to the crystallographic a axis
+
[O(2)Á Á ÁO(3i ) 2.556(4), O(2)–H(90) 0.77(4) A, O(2)–H(90)Á Á Á
O(3i ) 170(4)ꢁ; i: 1=2 þ x, 1=2 ꢀ y, 1 ꢀ z].
Crystal structure of (Sp)-4
Preparation and structure of complex 5
The molecular structure of the carboxyphosphine oxide (Sp)-4
(Fig. 2, Table 2) is similar to the structure of (S,Sp)-3, parti-
cularly when the arrangement of the 2-(diphenylphos-
phinoyl)ferrocenyl moiety is considered. The two units differ
only marginally in mutual rotation of the phenyl rings. Ferro-
cene cyclopentadienyls in (Sp)-4 are eclipsed with a t[C(1)–
Cg1–Cg2–C(6)] torsion angle of ꢀ5.7(2)ꢁ and show a tilt of
only 1.8(2)ꢁ. The dihedral angle subtended by the carboxyl
plane [C(11)O(1)O(2)] and its parent cyclopentadienyl ring is
7.7(4)ꢁ but the orientation of the carboxyl group is exactly the
opposite to that in (S,Sp)-3. This can be attributed to different
solid-state interactions: whereas the amide (S,Sp)-3 forms only
intramolecular hydrogen bonds and its solid-state packing is
Reacting [{RuCl(m-Cl)(Z6-p-cymene)}2] with (Sp)-Kpfc
generated in situ from (Sp)-Hpfc and tert-BuOK in dichloro-
methane–methanol produces a chelate complex [RuCl(pfc-
k2O,P)(Z6-p-cymene)], 5. The metal centre in 5 is stereogenic
due to its being surrounded by four different donors and,
consequently, the formation of two diastereoisomers could be
expected (Scheme 2). Surprisingly, the NMR analysis of a
recrystallized sample revealed the presence of a single dia-
stereoisomer whose absolute configuration was later deter-
mined as (RRu ,Sp) by X-ray crystallography (see below).
Following the metathesis reaction by NMR spectroscopy
(Fig. 3) has shown that both diastereoisomers are formed in a
ca. 1 : 1 kinetic ratio (dP 22.3 and 28.8 in CD2Cl2) but the
product distribution shifts slowly in favour of the thermo-
dynamically preferred isomer (RRu ,Sp)-5. Once formed, the
(RRu ,Sp)-isomer does not epimerize in chloroform-d or
dichloromethane-d2 solutions as indicated by the 31P{1H}
Fig. 2 Structure of (Sp)-4 at the 30% probability level. For clarity,
only labels of pivot and adjacent atoms in each ring are shown.
Scheme 2
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(S)-2-diphenylphosphinoyl-20-diphenylphosphino-1,10-binaph-
thyl (BINPO) give only one diastereoisomer23 and similar
reactions of C-chiral but racemic [RuCl2{Ph2PCH(R)P(O)Ph2-
kP}(Z6-p-cymene)] with Ag[SbF6] affords uniformly cationic
complexes [RuCl{Ph2PCH(R)P(O)Ph2-kP,O}(Z6-p-cymene)]-
[SbF6] (R ¼ Me, Pr, Ph) as single diastereoisomers with the
same relative configuration.24 In the case of related complexes
with chiral a-amino acidate ligands, [RuCl(H2NCHRCO2-
k2O,N)(Z6-arene)], the ratio of diastereoisomers changes with
the steric properties of the ligand and stabilization by hydrogen
bonding.25
In an attempt to identify steric factors possibly influencing
the diastereomeric equilibrium, the structure of (RRu ,Sp)-5 was
determined by single-crystal X-ray diffraction. Although no
solvent was detected in the bulk sample, the crystal obtained
by recrystallization from a dichloromethane–hexane mixture
contained loosely bound solvating dichloromethane. The sol-
vating molecules are disordered within channels parallel to the
crystallographic C4 axis in a space defined by the complex
molecules (see Experimental).
The molecular structure of (RRu ,Sp)-5 is shown in Fig. 4 and
selected geometric parameters are given in Table 3. The
molecule shows the anticipated three-legged piano stool
structure in which the (Sp)-pfcꢀ anion chelates the ruthenium
centre. The six-membered metallacycle [RuPC(2)C(1)C(11)-
O(2)] is almost perfectly planar; the maximum deviation of the
defining atoms from their least-squares plane is only 0.070(7)
A for C(11). The arene plane and the plane of the remaining
+
donor atoms [PClO(2)] do not deviate much from a co-planar
arrangement, the corresponding dihedral angle being 8.8(3)ꢁ.
The coordination environment around the ruthenium atom in
(RRu ,Sp)-5 is pseudo-octahedral with three sites occupied by
the fac-coordinated Z6-arene and, hence, a deviation of the
donor–Ru–donor angles from a right angle can be regarded as
the measure of coordination sphere deformation. The observed
values, maximum O(2)–Ru–P ¼ 92.8(1)ꢁ and minimum O(2)–
Ru–Cl ¼ 82.6(2)ꢁ, indicate that chelation does not affect the
Fig. 3 31P{1H} NMR spectra (CD2Cl2 , 298 K) recorded to follow
complex 5 formation: (a) (Sp)-Hpfc; (b) (Sp)-Kpfc prepared in situ from
(Sp)-Hpfc and tert-BuOK; a mixture of (RRu ,Sp)-5 (dP 22.3) and
(SRu ,Sp)-5 (dP 28.8) (c) after stirring (Sp)-Kpfc with [{RuCl(m-Cl)(Z6-p-
cymene)}2] for 3 and (d) after standing overnight; (e) spectrum of a
recrystallized sample [several days, (RRu ,Sp)-5].
NMR spectra. Pure (RRu ,Sp)-5 can thus be obtained by
simple recrystallization of the crude product from a dichloro-
methane–hexane mixture over several days (82% yield).
Apart from signals of the ferrocene ligand, the 1H and
13C{1H} NMR spectra of (RRu ,Sp)-5 exhibit diastereotopic
and remarkably anisochronic resonances of the arene ligand.
The fact that 1H NMR signals of only the arene ligand are
rather broad points to a hindered libration movement of the
Z6-ligand that is slow on the NMR time scale (in CDCl3
solution at room temperature).
Although no mechanistic study has been carried out, it
may be expected that the isomerization mechanism is initiated
by a pfc-k2O,P
pfc-kP interconversion analogous to the
!
fluxional behaviour of [Rh(CO)(dpf-k2O,P)(Hdpf-kP)] in
which the two forms of the Hdpf ligand rapidly interchange
the acidic hydrogen atom.17c Involvement of a pfc-kO inter-
mediate is less likely because the bond of ruthenium to the
hard oxygen donor is more labile than the bond between
soft ruthenium and phosphorus atoms. The position of the
isomerization equilibrium and, hence, diastereoselectivity
of the reaction obviously reflects steric properties of the
(Sp)-pfcꢀ anion since the diastereomeric ratio in similar reac-
tions varies greatly upon changing the chelate ligand. For
example, (R)-1-{2-(diphenylphosphino)naphthyl}isoquinoline
[(R)-Quinap] reacts with [{RuCl(m-Cl)(Z6-p-cymene)}2] and
Ag[SbF6], giving [RuCl-{(R)-Quinap-k2N,P}(Z6-p-cymene)]
[SbF6] as a 5 : 1 mixture of diastereoisomers.22 Analogous
reactions with the phosphine-phosphine oxides (R)- and
Fig. 4 Structure of (RRu ,Sp)-5Á0.7CH2Cl2 . Molecules of solvating
dichloromethane are not shown. As the atom numbering scheme is
similar to that of (Sp)-4, only selected atoms are labelled.
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a
Table 3 Selected geometric parameters (RRu ,Sp)-5 Á 0.7CH2Cl2
Concluding remarks
Fe–Cg1
1.650(3) Fe–C(Cp) ave.
1.632(4) C–C(Cp) ave.
1.697(4)
2.391(2) O(2)–Ru–P
2.325(2) O(2)–Ru–Cl
2.066(4) P–Ru–Cl
2.03(1)
1.41(2)
A series of planarly chiral ferrocene derivatives was obtained
from ferrocenecarboxylic acid via oxazoline (S,Sp)-1 by a
combination of oxazoline protecting and chiral ortho-directing
group approaches. The deprotonation of the key compound,
(Sp)-Hpfc, gives the (Sp)-pfcꢀ anion capable of chelating metal
centres. As exemplified by the synthesis of complex (RRu ,Sp)-5,
the steric properties of the phosphinocarboxylate ligand
induce highly diastereoselective chelation, yielding a thermo-
dynamically (sterically) preferred isomer after epimerization.
The mechanism of epimerization likely involves a reversible
Ru–O bond cleavage, a subsequent formal rotation around the
Ru–P bond and, finally, closure of the chelate ring. The pro-
posed course of isomerization is in accordance with the
expected differences in bond strengths between the soft
ruthenium(II) centre and the hard and soft donor atoms of the
hybrid ligand. Despite being formed in an equilibrium reac-
tion, the (RRu ,Sp)-5 diastereoisomer is stable to configura-
tional inversion at the metal centre in solution. This fact
becomes particularly important in view of the application of
chiral metal-based Lewis acids resulting from halogen
abstraction in systems similar to 5 as catalysts for asymmetric
Diels–Alder reactions30 or hydrogen transfer reduction of
ketones.31
Fe–Cg2
Ru–Cg3
Ru–Cl
Ru–P
Ru–O(2)
C(2)–P
P–C(12)
P–C(18)
C(1)–C(11)
C(11)–O(1)
C(12)–O(2)
Ru–C(arene)c
92.8(1)
82.6(2)
87.3(6)
1.816(6) Ru–P–C(2,12,18) 114.4(2)–118.8(2)
1.821(7) C–P–Cb
100.6(3)–109.0(3)
111.4(2)
124.8(4)
1.831(6) C(2)–P–Ru
1.508(8) C(1)–C(2)–P
1.256(8) C(3)–C(2)–P
1.271(8) O(1)–C(11)–O(2) 121.4(6)
2.171(6)– C(11)–O(2)–Ru 137.7(4)
2.269(7)
1.42(1)– C(5)–C(1)–C(11) 122.3(6)
1.44(1)
1.48(1) C(2)–C(1)–C(11) 130.0(6)
127.4(5)
C–C(arene)c
C(24)–C(30)
C(27)–C(31)
C(31)–C(32)
C(31)–C(33)
C(11)–C(1)–C(2)–P
C(2)–C(1)–C(11)–O(1)
C(2)–C(1)–C(11)–O(2)
C(1)–C(2)–P–Ru
Cp1,Cp2
1.45(2)
1.54(2)
1.50(1)
ꢀ6.1(9)
172.5(6)
ꢀ13(1)
ꢀ0.9(5)
2.9(4)
42.6(4)
70.5(4)
79.8(4)
Cym,Cp1
Cym,Ph1
Cym,Ph2
51.1(4)
45.6(4)
34.5(4)
Cp1,Ph1
Cp1,Ph2
Ph1,Ph2
Planes are defined as follows: Cp1, C(1–5); Cp2, C(6–10); Ph1, C(12–
17); Ph2, C(18–23), and Cym, C(24–29). Cg1 and Cg2 are centroids of
the cyclopentadienyl rings Cp1 and Cp2, respectively. Cg3 denotes the
a
Experimental
b
centroid of the C(24–29) Z6-arene plane. C(2)–P–C(12,18) and
Materials and methods
c
C(12)–P–C(18) angles. Z6-Arene moiety: C(24–29).
All reactions were carried under argon atmosphere. Tetra-
hydrofuran (THF) was dried by refluxing over potassium–
benzophenone under argon. Dichloromethane was stored over
potassium carbonate. Methanol, acetic anhydride and pyridine
were distilled under argon. Oxazoline (S,Sp)-111e and
[{RuCl(m-Cl)(Z6-p-cymene)}2]32 were prepared by literature
procedures. All other chemicals were used as received from
commercial suppliers.
NMR spectra were recorded on a Varian UNITY Inova 400
spectrometer (1H, 399.95; 13C, 100.58; 31P, 161.90 MHz) at
298 K. Chemical shifts (d) are given relative to internal tetra-
methylsilane (1H and 13C) or external 85% aqueous H3PO4
(31P). IR spectra were recorded on an FT IR Nicolet Magna
650 instrument in the range of 400–4000 cmꢀ1. Optical rota-
tions were measured on an automatic polarimeter Autopol III
(Rudolph Research, New Jersey; [a]D=deg cm3 gꢀ1 dmꢀ1, c=g
10ꢀ2 cmꢀ3). Fast atom bombardment (FAB) mass spectra
were measured on a ZB-SEQ VG Analytical spectrometer
(positive ion mode, Xe fast atoms, 8 kV, matrix: thioglycerol–
glycerol 3 : 1).
metal centre geometry in any significant way. Nevertheless, the
ligand bite angle O(2)–Ru–P in (RRu ,Sp)-5 is about 10ꢁ larger
than the angle in other structurally characterized complexes
with six-membered chelate rings.26 The Ru–donor bond
lengths compare well to, for instance, a complex with a che-
lating 2-acetamidocinnamate ligand, [Ru{OC(O)C(=CHPh)-
N(COMe)-k2O,N}(PPh3)(Z6-p-cymene)] [Ru–O 2.073(4), C–O
+
1.292(8), C=O 1.226(8) and Ru–P 2.356(2) A]27 the cationic
carbene [Ru{=C(CH2Fc)OMe}(Z6-p-cymene)(Hdpf-kP)]PF6
+
[Ru–Cl 2.390(3) and Ru–P 2.343(3) A],17b a phosphinophen-
oxide complex, [RuCl{3-MeO-2-(PPh[2,6-(MeO)2C6H3])-1-
OC6H3-k2O,P}(Z6-p-cymene)] [Ru–Cl 2.401(4), Ru–O 2.069(6)
+
and Ru–P 2.342(3) A]28 and the diruthenium(II) complex
[(m-dppf){RuCl2(Z6-1,2,3,4-Me4C6H2)}2]ÁCH2Cl2 [dppf ¼ 1,10-
bis(diphenylphosphino)ferrocene; Ru–P 2.350(4), Ru–Cl
+
2.404(5) and 2.400(3) A].29
Syntheses
The ferrocene unit in (RRu ,Sp)-5 remains virtually unaf-
fected by coordination. Its cyclopentadienyl rings are perfectly
eclipsed {t[C(1)–Cg1–Cg2–C(6)] ¼ ꢀ0.1(5)ꢁ} and show a tilt of
2.9(4)ꢁ. The ferrocene unit is directed away from the Ru(Z6-
arene) part so that the dihedral angle between the Cp1 and
arene least-squares planes is 51.1(1)ꢁ (see Table 3). The
arrangement of the diphenylphosphino moiety is significantly
distorted. The phenyl groups show different rotations with
respect to the substituted cyclopentadienyl plane Cp1 [dihedral
angles 42.6(4) and 70.5(4)ꢁ], likely conforming to steric
requirements of the arene ligand, which is rotated so as to
bring the bulky iso-propyl group to a less hindered position
away from the diphenylphosphinyl group. An inverted
arrangement of the phosphinocarboxylate ligand with the
PPh2 group directed away from the arene ligand would be
unfavourable due to crowding between the arene and the rigid
ferrocene unit.
(S,Sp)-2-Acetamido-3-methylbutyl 2-(diphenylphosphino)ferro-
cenecarboxylate, (S,Sp)-2. A mixture of water (0.90 cm3, 50
mmol) and anhydrous sodium sulfate (7.10 g, 50 mmol) was
carefully shaken up and suspended in THF (15 cm3). The
suspension was briefly stirred and oxazoline (S,Sp)-1 (0.481 g,
1.00 mmol) was added. When all the oxazoline had dissolved,
trifluoroacetic acid (0.39 cm3, 5.1 mmol) was added, causing the
colour of the supernatant to change from orange to red. After
stirring overnight in the dark, the mixture, once again orange,
was filtered to remove insoluble salts. The solid was washed
with THF and the combined THF solutions were evaporated
under reduced pressure at a temperature not exceeding 30 ꢁC
leaving a dark orange oil. The oil was dissolved in dichlor-
omethane (20 cm3), the solution cooled in an ice bath and
acetic anhydride (3.3 cm3, 35 mmol) followed by pyridine (6.6
cm3, 70 mmol) were slowly introduced. After stirring for a
New J. Chem., 2002, 26, 567–575
571

View Article Online
further 18 h at room temperature in the dark, the mixture was
carefully washed with 3 M HCl (3 Â 25 cm3), saturated aqu-
eous sodium hydrogencarbonate (3 Â 25 cm3) and finally with
water (25 cm3). The organic phase was dried over MgSO4 ,
evaporated and the residue purified by column chromato-
graphy (silica gel, acetate–dichloromethane, 1 : 2 v=v). A small
amount of unreacted oxazoline eluted first, followed by the
major band of the product. Evaporation and drying in vacuo (2
Torr, 80 ꢁC, 1 h) afforded pure (S,Sp)-2 as an orange solid
(note: orange glassy material that crystallizes upon standing
was obtained in several cases). Yield: 0.381 g, 70%.
vNH 3244 (m), 3214 (m); ester vC O 1710 (vs), amide I 1674 (vs),
=
20
amide II 1558 (br, m). [a]D ¼ ꢀ96.1ꢁ (c ¼ 1.0, CHCl3). Anal.
calcd. for C30H32FeNO4P: C, 64.64; H, 5.79; N, 2.51%.
Found: C, 64.88; H, 5.68; N, 2.55%.
(Sp)-2-(Diphenylphosphino)ferrocenecarboxylic acid, (Sp)-
Hpfc. Ester amide (S,Sp)-2 (271 mg, 0.50 mmol) was dissolved
in a mixture of THF (5 cm3) and methanol (5 cm3). An aqu-
eous 3 M sodium hydroxide solution (5 cm3, 15 mmol) was
added and the resulting orange solution was stirred at 50 ꢁC
overnight. The organic solvents were removed under reduced
pressure, the residue was acidified with aqueous 3 M HCl and
extracted with dichloromethane (3 Â 10 cm3). The combined
organic extracts were washed with water (2 Â 25 ml), dried
(MgSO4) and evaporated. The residue was purified by chro-
matography on silica gel using a dichloromethane-methanol
(20 : 1, v=v) mixture as the eluent. A small amount of methyl
(Sp)-2-(diphenylphosphino)ferrocenecarboxylate is eluted first
(ca. 7 mg, 3%; identified by NMR), followed by the product,
which was obtained after evaporation and drying in vacuo
(1 Torr, 60 ꢁC, 1 h) as a bright orange solid (192 mg, 93%).
1H NMR (CDCl3): d 3.79 (ddd, J ꢂ 2.6, 1.4, 0.9 Hz, 1 H,
C5H3 , H-3), 4.24 (s, 5 H, C5H5), 4.49 (ddd, J ꢂ 2.6, 2.6, 0.6 Hz,
1 H, C5H3 , H-4), 5.09 (ddd, J ꢂ 2.6, 1.5, 1.4 Hz, 1 H, C5H3 ,
H-5), 7.19–7.54 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d
71.27 (d, J ¼ 1.2 Hz, C5H5), 72.44 (C5H3 , C-4), 74.06 (d,
1JPC ¼ 15.9 Hz, C5H3 , C-2), 74.8 (C5H3 , C-5), 75.82 (d,
2JPC ¼ 4.9 Hz, C5H3 , C-3), 76.99 (d, 2JPC ¼ 15.9 Hz, C5H3 , C-
3
1H NMR (CDCl3): d 0.97 (d, JHH ¼ 6.7 Hz, 3 H, CHMe2),
3
1.06 (d, JHH ¼ 6.6 Hz, 3 H, CHMe2), 1.72 (s, 3 H, MeCO),
2.03–2.18 (m, 1 H, CHMe2), 3.71 (ddd, J ꢂ 2.6, 1.5, 1.0 Hz, 1
3
2
H, C5H3 , H-3), 3.83 (dd, JHH ¼ 3.0, JHH ¼ 11.2 Hz, 1 H,
3
CH2O), 3.88 [dddd, 3JHH ꢂ JHH ꢂ 8 (NH, CHMe2),
3
3JHH ꢂ JHH ꢂ 3 Hz (CH2), 1 H, CHNH], 4.18 (s, 5 H, C5H5),
4.51 (ddd, J ꢂ 2.6, 2.6, 0.6 Hz, 1 H, C5H3 , H-4), 4.62 (dd,
2
3JHH ¼ 3.0, JHH ¼ 11.3 Hz, 1 H, CH2O), 5.19 (ddd, J ꢂ 2.6,
1.5, 1.3 Hz, 1 H, C5H3 , H-5), 5.66 (br d, 1 H, NH), 7.11–7.52
(m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 19.52, 19.61
(CHMe2), 23.24 (MeCO), 29.34 (d, J ¼ 4.9 Hz, CHMe2), 53.70
(CHNH), 64.89 (CH2O), 71.05 (C5H5), 72.53 (C5H3 , C-4),
3
1
75.15 (d, JPC ¼ 1.8 Hz, C5H3 , C-5), 75.28 (d, JPC ¼ 17.4 Hz,
2
C5H3 , C-2), 75.64 (d, JPC ¼ 4.3 Hz, C5H3 , C-3), 77.55 (d,
2JPC ¼ 14.0 Hz, C5H3 , C-1), 128.23 (PPh2 , CHp), 128.35 (d,
3JPC ¼ 7.3 Hz, PPh2 , CHm), 128.39 (d, JPC ¼ 6.1 Hz, PPh2 ,
3
2
CHm), 129.53 (PPh2 , CHp), 131.77 (d, JPC ¼ 17.7 Hz, PPh2 ,
2
3
CHo), 135.29 (d, JPC ¼ 22.0 Hz, PPh2 , CHo), 137.46 (d,
1), 128.02 (PPh2 , CHp), 128.11 (d, JPC ¼ 12.2 Hz, PPh2 ,
1JPC ¼ 11.0 Hz, PPh2 , Cipso), 139.59 (d, 1JPC ¼ 12.2 Hz, PPh2 ,
3
CHm), 128.18 (d, JPC ¼ 12.8 Hz, PPh2 , CHm), 129.13 (PPh2 ,
3
2
Cipso), 169.73 (MeCO), 171.62 (d, JPC ¼ 2.8 Hz, CO2).
CHp), 132.20 (d, JPC ¼ 19.5 Hz, PPh2 , CHo), 135.04 (d,
31P{1H} NMR (CDCl3): d ꢀ14.9 (s). IR (Nujol): v~=cmꢀ1 vNH
1
2JPC ¼ 21.4 Hz, PPh2 , CHo), 137.91 (d, JPC ¼ 12.2 Hz, PPh2 ,
1
3240 (br m), ester vC O 1710 (vs), amide I 1639 (vs), amide
=
Cipso), 139.14 (d, JPC ¼ 11.6 Hz, PPh2 , Cipso), 177.12 (d,
22
II ꢂ 1560 (composite br m). [a]D ¼ ꢀ149.5ꢁ (c ¼ 1.0, CHCl3).
2JPC ¼ 2.4 Hz, CO2H). 31P{1H} NMR (CDCl3): d ꢀ17.4 (s). IR
(Nujol): v~=cmꢀ1 vC O 1712 (m), 1664 (vs). [a]D ¼ ꢀ257.6ꢁ
20
Anal. calcd. for C30H32FeNO3P: C, 66.55; H, 5.96; N, 2.59%.
Found: C, 66.17; H, 6.06; N, 2.57%.
=
(c ¼ 0.99, CHCl3). Anal. calcd. for C23H19FeO2P: C, 66.69; H,
4.62%. Found: C, 66.15; H, 4.71%.
(S,Sp)-2-Acetamido-3-methylbutyl 2-(diphenylphosphinoyl)ferro-
cenecarboxylate, (S,Sp)-3. Ester amide (S,Sp)-2 (108.8 mg, 0.20
mmol) was dissolved in acetone (5 cm3), the solution was
cooled in an ice bath and treated with excess 30% aqueous
hydrogen peroxide (0.5 cm3) for 1 h. Unreacted hydrogen
peroxide was destroyed by addition of 10% aqueous sodium
thiosulfate (1 cm3) and stirring for another 30 min; acetone
was evaporated under reduced pressure and the residue
extracted with CH2Cl2 . The combined organic extracts were
dried with magnesium sulfate and evaporated. The residue was
dissolved in a little hot ethyl acetate and the solution was
allowed to crystallize by hexane diffusion over several days to
give (S,Sp)-3 as fine yellow needles (84.2 mg, 76%).
(Sp)-2-(Diphenylphosphinoyl)ferrocenecarboxylic acid, (Sp)-4.
Aqueous hydrogen peroxide (5 drops of 30% solution) was
added to an ice-cooled solution of (Sp)-Hpfc (42 mg, 0.10
mmol) in acetone (2 cm3) with stirring. After stirring for
another 30 min at 0 ꢁC, excess hydrogen peroxide was
destroyed with 10% aqueous sodium thiosulfate (10 drops)
and stirring for 30 min at room temperature. Acetone was
removed under reduced pressure, and the residue was diluted
with water, acidified with 3 drops of 6 M HCl and extracted
into dichloromethane. The extract was dried over magnesium
sulfate and evaporated to give the phosphine oxide as an
orange yellow solid in quantitative yield (43 mg).
1H NMR (CDCl3): d 4.21 (ddd, J ꢂ 2.6, 2.6, 1.6 Hz, 1 H,
C5H3 , H-3), 4.26 (s, 5 H, C5H5), 4.71 (ddd, J ꢂ 2.6, 2.6, 1.8 Hz,
1 H, C5H3 , H-4), 5.39 (ddd, J ꢂ 2.6, 1.4, 1.4 Hz, 1 H, C5H3 ,
H-5), 7.38–7.92 (m, 10 H, PPh2), 14.07 (s, 1 H, CO2H). 13C{1H}
3
1H NMR (CDCl3): d 1.03, 1.08 (2 Â d, JHH ¼ 6.7 Hz, 3 H,
CHMe2); 1.88 (d of septets, 3JHH ¼ 10.4, 6.7 Hz, 3 H, CHMe2),
2
3
2.13 (s, 3 H, MeCO), 2.94 (dd, JHH ¼ 11.2, JHH ¼ 2.6 Hz, 1
H, CH2O), 3.75 (br dddd, J ꢂ 1.6, 2.6, 10, 10 Hz, 1 H,
CHMe2), 3.79 (ddd, J ꢂ 2.6, 1.3, 1.0 Hz, C5H3 , H-3), 4.49 (s, 5
H, C5H5), 4.58 (ddd, J ꢂ 2.6, 2.6, 0.8 Hz, 1 H, C5H3 , H-4),
1
NMR (CDCl3): d 70.78 (d, JPC ¼ 112 Hz, C5H3 , C-2), 71.51
(d, 2JPC ¼ 13 Hz, C5H3 , C-1), 71.87 (C5H5), 74.18 (d, 3JPC ¼ 11
Hz, C5H3 , C-4), 76.37 (d, 2JPC ¼ 13 Hz, C5H3 , C-3), 76.84 (d,
2
3
5.09 (dd, JHH ¼ 11.2, JHH ¼ 1.6 Hz, 1 H, CH2O), 5.30 (ddd,
J ꢂ 2.6, 1.3, 1.3 Hz, 1 H, C5H3 , H-5), 7.30–7.72 (m, 10 H,
PPh2), 9.11 (d, J ¼ 9.6 Hz, 1 H, NH). 13C{1H} NMR (CDCl3):
d 19.91, 19.96 (CHMe2), 23.32 (MeCO), 29.14 (CHMe2), 54.17
(CHNH), 64.41 (CH2O), 71.45 (C5H5), 72.98 (d, 3JPC ¼ 12 Hz,
3
3JPC ¼ 8 Hz, C5H3 , C-5), 128.73, 128.73 (2 Â d, JPC ¼ 13 Hz,
1
PPh2 , CHm); 129.71 (d, JPC ¼ 111 Hz, PPh2 , Cipso), 131.38,
131.85 (2 Â d, 2JPC ¼ 10 Hz, PPh2 , CHo); 132.21 (d, 1JPC ¼ 107
4
Hz, PPh2 , Cipso), 132.66 (d, JPC ¼ 2 Hz, PPh2 , CHp), 133.07
4
(d, JPC ¼ 3 Hz, PPh2 , CHp), 170.27 (CO2H). 31P{1H} NMR
1
C5H3 , C-4), 73.94 (d, JPC ¼ 81 Hz, C5H3 , C-2), 74.53 (d,
(CDCl3): d 38.3 (s). IR (Nujol): v~=cmꢀ1 vC¼O 1692 (vs).
3
2JPC ¼ 23 Hz, C5H3 , C-1), 76.28 (d, JPC ¼ 8 Hz, C5H3 , C-5),
20
[a]D ¼ ꢀ37.3ꢁ (c ¼ 0.7, CHCl3). Anal. calcd. for
2
80.21 (d, JPC ¼ 15 Hz, C5H3 , C-3), 128.19, 128.31 (2 Â d,
C23H19FeO3P: C, 64.21; H, 4.45%. Found: C, 63.61; H, 4.38%.
2
3JPC ¼ 9 Hz, PPh2 , CHm), 131.15 (d, JPC ¼ 10 Hz, PPh2 ,
4
CHo), 131.70, 131.76 (2 Â d, JPC ¼ 2 Hz, PPh2 , CHp), 131.80
(d, 2JPC ¼ 10 Hz, PPh2 , CHo), 133.61 (d, 1JPC ¼ 110 Hz, PPh2 ,
(RRu ,Sp)-Chloro[2-(diphenylphosphino)ferrocenecarboxylato-
k2O,P]{h6-1-methyl-4-(1-methylethyl)benzene}ruthenium(II),
(RRu ,Sp)-5. (Sp)-Hpfc (44.2 mg, 0.11 mmol) and potassium
1
Cipso), 133.63 (d, JPC ¼ 110 Hz, PPh2 , Cipso), 169.95, 170.11
(CO). 31P{1H} NMR (CDCl3): d 31.8 (s). IR (Nujol): v~=cmꢀ1
572
New J. Chem., 2002, 26, 567–575

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tert-butoxide (12.2 mg, 0.11 mmol) were dissolved in methanol
(2 cm3) and stirred for 30 min at room temperature. Then, a
solution of di-m-chloro-bis{chloro(Z6-p-cymene)ruthenium(II)}
(30.6 mg, 50 mmol) in dichloromethane (2 cm3) was added to
the resulting solution of (Sp)-Kpfc. A fine precipitate formed
immediately. After the mixture had been stirred for 3 h, the
solvents were evaporated under reduced pressure and the solid
residue extracted with dichloromethane (2 Â 1 cm3). The
extract was filtered through a Celite pad to remove pre-
cipitated KCl and the clear filtrate was allowed to crystallize
by liquid-phase diffusion of excess hexane over several days at
ꢀ18 ꢁC in the dark to give (RRu ,Sp)-5 as a greenish brown
solid (55.8 mg, 82%).
cated a complete conversion of (Sp)-Hpfc to (Sp)-Kpfc. Then,
[{RuCl(m-Cl)(Z6-p-cymene)}2] (9.5 mg, 15 mmol) was added
and the mixture was analyzed by NMR spectroscopy. The
31P{1H} NMR spectra of a freshly prepared sample showed
two signals at dP 22.3 and 28.8 in a ca. 1 : 1 ratio. Upon
standing, the ratio changes in favour of the former resonance
(see Fig. 3). NMR data for CD2Cl2 solutions, (Sp)-Hpfc: dH
3.80, 4.53, 5.10 (3 Â m, 2 H, C5H3), 4.24 (s, 5 H, C5H5), 7.13–
7.54 (m, 10 H, PPh2), dP ꢀ17.7 (s); (Sp)-Kpfc: dH 3.57, 4.35,
5.01 (3 Â m, 2 H, C5H3), 4.22 (s, 5 H, C5H5), 6.98–7.52 (m, 10
H, PPh2); dP ꢀ16.2 (s).
To prepare complex 5 (Sp)-Hpfc (20.7 mg, 50 mmol) and tert-
BuOK (6.5 mg, 58 mmol) were dissolved in methanol (1 cm3).
After stirring for 30 min at room temperature, a solution of
[{RuCl(m-Cl)(Z6-p-cymene)}2] (15.3 mg, 25 mmol) in dichlor-
omethane (1 cm3) was added and stirring was continued for
another for 3 h. Then, all volatiles were removed in vacuum,
the brown residue was extracted with CD2Cl2 (0.7 cm3) and the
extract was analyzed by NMR spectroscopy after standing
overnight. 31P{1H} NMR (CD2Cl2): dP 22.3 (s, ꢂ82%), 28.8
(s, ꢂ17%).
3
1H NMR (CDCl3): d 0.89 (d, JHH ¼ 6.8 Hz, 3 H, CHMe2),
3
1.13 (d, JHH ¼ 7.1 Hz, 3 H, CHMe2), 2.03 (s, 3 H, Me), 2.62
3
(sept, JHH ¼ 6.9 Hz, 1 H, CHMe2), 3.99 (s, 5 H, C5H5), 4.21
(dt, J ꢂ 2.6, 1.4, 1.4 Hz, 1 H, C5H3 , H-5), 4.33 (br dt, J ¼ 5.7
Hz, 1 H, C6H4 , H-3), 4.44 (t, J ꢂ 2.6 Hz, 1 H, C5H3 , H-4),
5.18 (br dd, J ¼ 5.5, 1.9 Hz, 1 H, C6H4 , H-2), 5.32 (br d,
J ¼ 6.3 Hz, 1 H, C6H4 , H-6), 5.35 (dt, J ꢂ 1.4, 1.4, 2.5 Hz, 1 H,
C5H3 , H-3), 5.69 (br d, J ¼ 6.4 Hz, 1 H, C6H4 , H-5), 7.10–8.30
(m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 18.01 (Me), 21.07,
1
22.75 (CHMe2), 29.86 (CHMe2), 69.32 (d, JPC ¼ 51 Hz,
X-Ray Crystallography
3
C5H3 , C-2), 71.73 (C5H5), 72.42 (d, JPC ¼ 6 Hz, C5H3 , C-4),
72.44 (C5H3 , C-5), 75.81 (d, 2JPC ¼ 8 Hz, C5H3 , C-3), 83.83 (d,
2JPC ¼ 16 Hz, C5H3 , C-2), 85.09 (d, JPC ¼ 2 Hz, C6H4 , C-2),
86.81 (d, JPC ¼ 2 Hz, C6H4 , C-3), 90.54 (d, JPC ¼ 8 Hz, C6H4 ,
C-5), 93.89 (C6H4 , C-1), 98.17 (d, JPC ¼ 7 Hz, C6H4 , C-6),
107.46 (C6H4 , C-4), 128.03, 128.22 (2 Â d, 3JPC ¼ 11 Hz, PPh2 ,
Diffraction data for compound (S,Sp)-3 (Table 4) were col-
lected on a Nonius KappaCCD image plate diffractometer
using graphite monochromated Mo-Ka radiation (l ¼ 0.71073
+
A): 277 frames were measured (1.8ꢁ o oscillation and 81 s
counting time each, 40181 integrated diffractions) and ana-
lyzed with HKL program package.33 Cell parameters were
determined by least-squares fitting from 30385 partial diffrac-
tions with 1.0 4 y 4 27.1ꢁ. The structure was solved by direct
methods (SIR9234) and refined by full-matrix least-squares on
F2 (SHELXL9735). Non-hydrogen atoms were refined aniso-
tropically. All hydrogen atoms were identified on difference
electron density maps and refined with isotropic displacement
parameters.
4
2
CHm); 129.84 (d, JPC ¼ Hz, PPh2 , CHp), 131.14 (d, JPC ¼ 9
4
Hz, PPh2 , CHo), 131.55 (d, JPC ¼ 2 Hz, PPh2 , CHp), 131.68
(d, 1JPC ¼ 53 Hz, PPh2 , Cipso), 135.57 (d, JPC ¼ 11 Hz, PPh2 ,
2
1
CHo), 141.95 (d, JPC ¼ 51 Hz, PPh2 , Cipso), 174.19 (CO).
31P{1H} NMR (CDCl3): d 22.1 (pfcꢀ). FABþ: m=z 685.3
([M þ H]þ, C33H33ClFeO2PRu).
In situ NMR study. Preparation of (Sp)-Kpfc and complex 5
Diffraction data for compound (Sp)-4 (Table 4) were col-
lected as for (S,Sp)-3 except that 102 frames were measured
(2.0ꢁ o oscillation and 180 s counting time, 11 558 integrated
diffractions) and the cell parameters were determined from
(Sp)-Hpfc (11.5 mg, 28 mmol) and tert-BuOK (3.5 mg, 31 mmol)
were dissolved in CD2Cl2 and allowed to stand for 30 min at
room temperature. NMR spectroscopy of the mixture indi-
Table 4 Crystallographic data, data collection and structure refinement for compounds (S,Sp)-3, (Sp)-4, and (RRu ,Sp)-5Á0.7CH2Cl2
(S,Sp)-3
C30H32FeNO4P
557.39
(Sp)-4
(RRu ,Sp)-5Á0.7CH2Cl2
Formula
C23H19FeO3P
430.20
150
Orthorhombic
P212121 (No. 19)
8.7508(3)
14.1915(6)
15.6483(8)
90
1943.3(2)
4
0.880
3383
3101
0=10, 0=16, ꢀ18=18
3.0–25.0
0.0311, 1.4405
ꢀ0.05(2)
3.63
7.85
4.46
8.28
4.8
C33.7H33.4Cl2.4FeO2PRue
743.37
Formula wt
T=K
Crystal system
150
150
Tetragonal
P41212 (No. 92)
23.9653(2)
23.9653(2)
11.3015(1)
90
6490.9(1)
8
1.188
5727
5328
Orthorhombic
P212121 (No. 19)
8.5942(1)
16.0218(3)
19.5448(3)
90
2691.21(7)
4
0.656
Space group
+
a=A
+
b=A
+
c=A
a ¼ b ¼ g=ꢁ
+
U=A3
Z
m(Mo-Ka)=mmꢀ1
No. unique diffractions
No. observed diffractionsa
hkl range
5920
5314
0=10, 0=20, ꢀ24=25
3.2–27.1
0.0309, 1.3860
ꢀ0.02(1)
3.33
7.02
4.25
7.41
4.7
ꢀ26=28, ꢀ28=28, ꢀ13=12
y range=ꢁ
3.0–25.0
0.0930, 6.5210
0.01(4)
4.95
b
w1, w2
Flack’s enantiomorph parameter
R for obsd diffractionsc (%)
wR for obsd diffractionsc (%)
R for all datac (%)
14.3
5.39
14.6
5.8
wR for all datac (%)
d
Rint
+
Residual electron density=eAꢀ3
0.21, ꢀ0.36
0.21, ꢀ0.38
0.64, ꢀ0.74
a
b
c
Diffractions with Io > 2s(Io). Weighting scheme: w ¼ [s2(Fo2) þ (w1P)2 þ w2P]ꢀ1, where P ¼ 1=3[max(Fo2) þ 2Fc2]. R(F) ¼ SkFoj ꢀ jFck=
SjFoj, wR(F2) ¼ [S{w(Fo ꢀ Fc2)2}={Sw(Fo2)2}]1=2
.
Rint ¼ SjFo ꢀ Fo,mean j=SFo
.
C33H32ClFeO2PRuÁ0.70CH2Cl2 .
2
d
2
2
2
e
New J. Chem., 2002, 26, 567–575
573

View Article Online
10 490 partial diffractions with 1.0 4 y 4 25.0ꢁ. The structure
was solved and refined as given above. All non-hydrogen
3
The first non-racemic planarly chiral ferrocene derivative was
reported in 1959; J. B. Thompson, Tetrahedron L ett., 1959, 26. For
a review about applications of chiral ferrocene ligands in homo-
geneous catalysis see, for instance: (a) Ferrocenes, ed. A. Togni
and T. Hayashi, VCH, Weinheim, 1995; (b) C. J. Richards and
A. J. Locke, Tetrahedron: Asymmetry, 1998, 9, 2377; (c) H. B.
Kagan, P. Diter, A. Gref, D. Guillaneux, A. Masson-Szymczak,
atoms were refined anisotropically. Aromatic hydrogen atoms
were fixed in calculated positions with C–H 0.93 A and
+
Uiso(H) ¼ 1.2 Ueq(C). The carboxylic hydrogen atom was
identified on a difference electron density map and refined
isotropically.
F. Rebiere, O. Riant, O. Samuel and S. Taudien, Pure Appl.
`
Chem., 1996, 68, 29; (d) A. Togni, Angew. Chem., Int. Ed. Engl.,
1996, 35, 1475.
V. Snieckus, Chem. Rev., 1990, 90, 879.
(a) D. W. Slocum, B. W. Rockett and C. R. Hauser, Chem. Ind.
(L ondon), 1964, 1831; (b) D. W. Slocum, B. W. Rockett and C. R.
Hauser, J. Am. Chem. Soc., 1965, 87, 1241.
Diffraction data for complex (RRu ,Sp)-5 (Table 4) were
collected similarly to those of (S,Sp)-3: 340 frames (1.4ꢁ
o
4
5
oscillation and 210 s counting time each, 90 565 integrated
diffractions). Cell parameters were determined by least-squares
refinement from 115 407 partial diffractions with 1.0 4 y 4
25.0ꢁ. The diffraction data were corrected for absorption
(Tmin ¼ 0.609, Tmax ¼ 0.800; numerical method, SORTAV
routine incorporated in the program package by Nonius BV).
The structure was solved and refined as described above. The
non-hydrogen atoms of the complex molecule were refined
anisotropically whilst all hydrogen atoms were included in
6
7
D. Marquarding, H. Klusacek, G. Gokel, P. Hoffmann and
I. Ugi, J. Am. Chem. Soc., 1970, 92, 5389.
Some representative examples: (a) T. Hayashi, T. Mise, M.
Fukushima, M. Kagotani, N. Nagashima, Y. Hamada, A.
Matsumoto, S. Kawakami, M. Konishi, K. Yamamoto and M.
Kumada, Bull. Chem. Soc. Jpn., 1980, 53, 1138; (b) T. Hayashi,
Pure Appl. Chem., 1988, 60, 7 and references therein; (c) A. Togni,
C. Breutel, A. Schnyder, F. Spindler, F. Landert and A. Tijani,
J. Am. Chem. Soc., 1994, 116, 4062; (d) U. Burckhardt, L.
Hintermann, A. Schnyder and A. Togni, Organometallics, 1995,
14, 5415; (e) A. Schnyder, A. Togni and U. Wiesli, Organo-
metallics, 1997, 16, 255; ( f ) U. Burckhardt, M. Baumann, G.
Trabesinger, V. Gramlich and A. Togni, Organometallics, 1997,
calculated positions with fixed C–H bond lengths (methyl 0.96,
methine 0.98 and aromatic 0.93 A) and assigned Uiso(H) ¼
+
1.2 Ueq(C).
Difference electron density maps revealed a partial inclusion
of solvent molecules. The disordered solvate was modelled as if
consisting of three rigid CH2Cl2 moieties with constrained
geometry and ocuppancies set to 0.40, 0.15 and 0.15, respec-
tively, to give reasonable isotropic thermal motion parameters
and low R values (two molecules are found in a special posi-
tion with the ideal occupancy of 0.50). Although the model fits
well the diffraction data, the extremes on the residual electron
density map that are located in the space accommodating the
solvate molecules indicate the real situation to be even more
complicated than the model.
16, 5252; (g) A. Togni, R. Dorta, C. Kollner and G. Pioda, Pure
¨
Appl. Chem., 1998, 70, 1477 and references therein; (h) B. Gotov,
ˇ
S. Toma and D. J. Macquarrie, New J. Chem., 2000, 24, 597; (i)
M. Sawamura and Y. Ito, Chem. Rev., 1992, 92, 857; ( j ) H. U.
Blaser and F. Spindler, Top. Catal., 1997, 4, 275 (industrial ap-
plications).
8
Sulfoxides: (a) F. Rebiere, O. Riant, L. Ricard and H. B. Kagan,
`
Angew. Chem., Int. Ed. Engl., 1993, 32, 3568; (b) O. Riant, G.
Argouarch, D. Guillaneux, O. Samuel and H. B. Kagan, J. Org.
Chem., 1998, 63, 3511; (c) H. L. Pedersen and M. Johannsen,
Chem. Commun., 1999, 2517; Acetals: (d) O. Riant, O. Samuel and
H. B. Kagan, J. Am. Chem. Soc., 1993, 115, 5835; (e) O. Riant, O.
Samuel, T. Flessner, S. Taudien and H. B. Kagan, J. Org. Chem.,
1997, 62, 6733; ( f ) G. Argouarch, O. Samuel and H. B. Kagan,
Eur. J. Inorg. Chem., 2000, 2885; (g) G. G. A. Balavoine, J.-C.
Daran, G. Iftime, P. G. Lacroix, E. Manoury, J. A. Delaire, I.
Maltey-Fanton, K. Nakatani and S. Di Bella, Organometallics,
1999, 18, 21; (h) G. Iftime, J.-C. Daran, E. Manoury and G. G. A.
Balavoine, J. Organomet. Chem., 1998, 565, 115; (i) G. Iftime, J.-C.
Daran, E. Manoury and G. G. A. Balavoine, Organometallics,
1996, 15, 4808. Hydrazones: ( j ) C. Ganter and T. Wagner, Chem.
Ber., 1995, 128, 1157; (k) D. Enders, R. Peters, R. Lochtman and
J. Runsink, Eur. J. Inorg. Chem., 2000, 2839; (l) D. Enders, R.
Peters, R. Lochtman, G. Raabe, J. Runsink and J. W. Bats, Eur.
J. Inorg. Chem., 2000, 3399.
CCDC reference numbers 167918–167920. See http:==www.
rsc.org=suppdata=nj=b1=b109495p= for crystallographic data
in CIF or other electronic format.
Acknowledgements
Special thanks are due to Dr I. Cısarova from the Centre of
´ ˇ ´
Molecular and Crystal Structures, Charles University, for
measurement of the X-ray diffraction data. This work was
supported by Grant Agency of the Czech Republic (grant no.
203=01=P002, 203=99=M037) and is a part of a long-term
Research plan of the Faculty of Sciences, Charles University.
9
(a) P. von Matt and A. Pfaltz, Angew. Chem., Int. Ed. Engl., 1993,
32, 566; (b) G. Helmchen and A. Pfaltz, Acc. Chem. Res., 2000, 33,
336; (c) O. Reiser, Angew. Chem., Int. Ed. Engl., 1993, 32, 547; (d)
A. Pfaltz, Synlett, 1999, 835; (e) R. Pretoˆ t, G. C. Lloyd-Jones and
´
A. Pfaltz, Pure Appl. Chem., 1998, 70, 1035; ( f ) A. J. Blacker,
M. L. Clarke, M. S. Loft, M. F. Mahon, M. E. Humphries and
J. M. Williams, Chem. Eur. J., 2000, 6, 353.
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New J. Chem., 2002, 26, 567–575
575